[Cleanup] Move fd.a out of coefficientProduct

dune/tectonic/frictionpotential.hh

@@ -32,7 +32,7 @@ class FrictionPotentialWrapper {
 class FrictionPotential : public FrictionPotentialWrapper {
 public:
   FrictionPotential(double coefficient, FrictionData const &fd)
-      : fd(fd), coefficientProduct(coefficient * fd.a * fd.normalStress) {}
+      : fd(fd), weightTimesNormalStress(coefficient * fd.normalStress) {}
 
   double evaluate(double V) const {
     assert(V >= 0);
@@ -40,7 +40,7 @@ class FrictionPotential : public FrictionPotentialWrapper {
       return 0;
 
     // V log(V/V_m) - V + V_m
-    return coefficientProduct * (V * std::log(V / V_m) - V + V_m);
+    return weightTimesNormalStress * fd.a * (V * std::log(V / V_m) - V + V_m);
   }
 
   // log(V/V_m)  if V >= V_0
@@ -50,7 +50,7 @@ class FrictionPotential : public FrictionPotentialWrapper {
     if (V <= V_m)
       return 0;
 
-    return coefficientProduct * std::log(V / V_m);
+    return weightTimesNormalStress * fd.a * std::log(V / V_m);
   }
 
   // 1/V        if V >  V_0
@@ -61,7 +61,7 @@ class FrictionPotential : public FrictionPotentialWrapper {
     if (V <= V_m)
       return 0;
 
-    return coefficientProduct / V;
+    return weightTimesNormalStress * fd.a / V;
   }
 
   double regularity(double V) const {
@@ -83,7 +83,7 @@ class FrictionPotential : public FrictionPotentialWrapper {
 
 private:
   FrictionData const &fd;
-  double const coefficientProduct;
+  double const weightTimesNormalStress;
   double V_m;
 };